netdev - Re: [PATCH v3 bpf-next] net: veth: alloc skb in bulk for ndo_xdp

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Date:   Tue, 2 Feb 2021 15:14:00 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, davem@...emloft.net,
        kuba@...nel.org, ast@...nel.org, daniel@...earbox.net,
        toshiaki.makita1@...il.com, lorenzo.bianconi@...hat.com,
        toke@...hat.com, brouer@...hat.com
Subject: Re: [PATCH v3 bpf-next] net: veth: alloc skb in bulk for
 ndo_xdp_xmit

On Fri, 29 Jan 2021 23:04:08 +0100
Lorenzo Bianconi <lorenzo@...nel.org> wrote:

> Split ndo_xdp_xmit and ndo_start_xmit use cases in veth_xdp_rcv routine
> in order to alloc skbs in bulk for XDP_PASS verdict.
> Introduce xdp_alloc_skb_bulk utility routine to alloc skb bulk list.
> The proposed approach has been tested in the following scenario:
> 
> eth (ixgbe) --> XDP_REDIRECT --> veth0 --> (remote-ns) veth1 --> XDP_PASS
> 
> XDP_REDIRECT: xdp_redirect_map bpf sample
> XDP_PASS: xdp_rxq_info bpf sample
> 
> traffic generator: pkt_gen sending udp traffic on a remote device
> 
> bpf-next master: ~3.64Mpps
> bpf-next + skb bulking allocation: ~3.79Mpps
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---

I wanted Lorenzo to test 8 vs 16 bulking, but after much testing and
IRC dialog, we cannot find and measure any difference with enough
accuracy. Thus:

Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>

> Changes since v2:
> - use __GFP_ZERO flag instead of memset
> - move some veth_xdp_rcv_batch() logic in veth_xdp_rcv_skb()
> 
> Changes since v1:
> - drop patch 2/3, squash patch 1/3 and 3/3
> - set VETH_XDP_BATCH to 16
> - rework veth_xdp_rcv to use __ptr_ring_consume
> ---
>  drivers/net/veth.c | 78 ++++++++++++++++++++++++++++++++++------------
>  include/net/xdp.h  |  1 +
>  net/core/xdp.c     | 11 +++++++
>  3 files changed, 70 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 6e03b619c93c..aa1a66ad2ce5 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -35,6 +35,7 @@
>  #define VETH_XDP_HEADROOM	(XDP_PACKET_HEADROOM + NET_IP_ALIGN)
>  
>  #define VETH_XDP_TX_BULK_SIZE	16
> +#define VETH_XDP_BATCH		16
>  


-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer